Epithelium is one of the four basic types of animal tissues, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line surfaces and cavities throughout the body. Epithelium forms part of both the outside surface (skin) and the inside cavities and lumen of mammalian bodies. Functions of epithelial cells include protection, detection of sensation, selective absorption, secretion and transcellular transport.
The skin comprises stratified squamous, keratinized epithelial cells and viable keratinocytes among other cell types. Tissues lining the inside of the mouth, the esophagus and part of the rectum are composed of non-keratinized stratified squamous epithelium. Other surfaces that separate body cavities from the outside environment are padded by simple squamous, columnar, or pseudo-stratified epithelial cells. Other epithelial cells line the inside of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, and make up the exocrine and endocrine glands. The outer surface of the cornea is covered with fast-growing, easily regenerated epithelial cells.
In these organs and tissues, the epithelium serves as part of the protective barrier against harmful physical forces, chemicals, pollutants, pathogens and other undesired agents. All of these exogenous aggravations must challenge the epithelium before entering into the body.
Pollution born toxins have detrimental effect on the health of cells and tissues and on organs comprising same. Pollution may be caused by a vast number of a variety of factors, including, for example, indoor pollution resulting from cigarette smoke, cleaning products and dust, and outdoor pollution including engine smoke, industrial waste and carbon monoxide.
Toxic buildup is known to impair an organ's normal physiologic functions. The constant, sometimes daily exposure to environmental toxins leads to accumulated damage in the cells of all exposed organs. Common cellular mechanism by which most pollutants exert their adverse effects include their ability to act directly as pro-oxidants of lipids and proteins, form DNA adducts, DNA breakage or mutations or to act as free radicals generators, promoting oxidative stress and the induction of inflammatory responses.
Free radicals (reactive oxygen and nitrogen species) are harmful to cellular lipids, proteins, and nuclear- or mitochondrial-DNA, inhibiting their normal function. In addition, they can interfere with signaling pathways within cells. In eukaryotic aerobic organisms including humans, free radicals are continuously generated during normal metabolism and in response to exogenous environmental exposures (e.g. irradiation, cigarette smoke, metals and ozone). A state of oxidative stress occurs when the organism defense mechanisms are overwhelmed leading to an increase in the free radical concentration. This oxidative stress has been shown to be linked with poor appearance and premature aging of the skin. Oxidative stress has also been implicated in a wide variety of degenerative diseases such as atherosclerosis, heart attacks, stroke, chronic inflammatory diseases (rheumatoid arthritis), cataract, central nervous system disorders (Parkinson and Alzheimer's diseases), age related disorders and cancer.
Pollutants mainly reach mammalian tissues via dermal contact, inhalation and ingestion of contaminated products. Air and soil pollution contributes, to a great extent, to the contamination of food and water, such that ingestion is also a route of pollutant intake. Pollutants deposited in the gastrointestinal and respiratory tracts may be absorbed by the epithelial cells such that toxic substances appear in the general circulation and accumulate in different tissues.
The link between exposure to certain substances and epithelium damage is universally accepted. For example, formaldehyde is now recognized worldwide as both a carcinogen and a skin sensitizer. Another example is the pollutant chemicals found in tobacco smoke. Cigarette smoke contains over 4,700 chemical compounds of which about 60 have been designated as carcinogenic. People who smoke on a regular basis are prone to a damage of tissue comprising epithelial cells, particularly of the lung, oral cavity and skin. Aging processes of smoker's skin are also accelerated.
All types of pollution, at high concentration, can affect mammalian airways and gastrointestinal tract. Nevertheless, similar effects are also observed with long-term exposure to lower pollutant concentrations. Symptoms such as nose and throat irritation, followed by bronchoconstriction and dyspnoea, especially in asthmatic individuals, are usually experienced after exposure to increased levels of sulphur dioxide, nitrogen oxides, and certain heavy metals such as arsenic, nickel or vanadium. Air pollutants such as nitrogen oxides increase the susceptibility to respiratory infections. Chronic exposure to ozone and certain heavy metals reduces lung function, while the later are also responsible for asthma, emphysema, and even lung cancer. Emphysema-like lesions have also been observed in mice exposed to nitrogen dioxide
The epithelium possesses a limited active toxin defense including physical removal of exogenous toxins. Exemplary routes include the natural expulsion of contaminated cells as part of skin's organic turn-over and dissolving of toxins from interstitial spaces and transferring these back onto the surface via sweat. However, the natural defense mechanisms against toxins do not provide full protection.
Toxins that have not been physically removed may be metabolized within the epithelium. In recent years it has been demonstrated that human epithelium cells express various Cytochrome P450 (CYP) enzymes, including such that are responsible specifically for metabolism of exogenous toxins within various types of epithelial cells. The resulting metabolites may potentially also damage the epithelium and body. Defense against skin toxins depends on several factors, including behavioral routines (i.e., avoidance of exposure, diet) and use of traditional medicine, therapeutic and/or cosmetic products.
Traditional medicine has long appreciated the negative effect of toxin deposit on health and wellbeing and practices detoxification of the body as standard treatment for many diseases and disorders. Similar practices, with some variations, are very commonly self-implemented by the public. These detoxification processes focus on reducing the exposure to toxins and increasing removal of toxins from the body.
Skin is the largest and the most exposed organ of the body comprising epithelial tissues. Skin has numerous functions, the primary function being a protective barrier against harmful physical forces, chemicals, pollutants, pathogens and other undesired agents. The skin consists of three main layers: the epidermis, the outermost layer of skin, which provides a waterproof barrier and creates the skin tone; the dermis, which contains tough connective tissue, hair follicles, and sweat glands; and the deeper subcutaneous tissue (hypodermis), which is made of fat and connective tissue. The epidermis is further subdivided into several layers: the stratum corneum, the stratum granulosum, the stratum spinosum, and the stratum basale.
The genus Asteriscus (Tribe Inuleae, family Asteraceae) consists of eight species and five sub-species, the morphology, phylogeny, and phytogeography of which have been studied. Asteriscus graveolens (Forssk.) Less., has the synonyms Bubonium graveolens, Odontospermum graveolens, or Nauplius graveolens. This species, an endemic herbaceous medicinal aromatic plant, extends from North Africa to the desert regions of Asia. It has been used in Sahara folk medicine as a stomachic, for treating fever, gastrointestinal tract complaints, headache and bronchitis, and as an anti-inflammatory agent. The chemical composition of A. graveolens essential oils was recently described by Cristofari et al. (Cristofari G et al. 2012. Chemistry and Biodiversity 9:727-738). Traditional Chinese medicine preparations comprising a mixture of dried plant material including plants of the Asteraceae family, particularly of A. pseudosciaenae have been disclosed (for example, Chinese Applications No. CN104208618, CN104274770, CN10289555). Terthiophenes and polyynes from Asteraceae species have been suggested as components in plant-derived compositions for treating herpes and cold sores (International (PCT) Application Publication No. WO2015/034665).
International (PCT) Application Publication No. WO2014/006626 discloses the use of A. graveolens extract, among extracts of other plants, as pest repellent.
There is an ongoing attempt to develop plant-based compositions for treating skin disorders and damages. For example, U.S. Patent Application Publication No. 2007/0122492 discloses plant extracts and dermatological formulations comprising one or more plant extracts that are capable of inhibiting extracellular proteases. Also disclosed is the use of the plant extracts as dermatological agents suitable for treating or preventing various dermatological conditions, including wrinkling or sagging of the skin, irradiation induced skin and/or hair damage, deepening of skin lines, elastotic changes in the skin, as well as for the routine care of the skin, hair and/or nails.
U.S. Pat. No. 8,771,758 discloses a method of improving the aesthetic appearance of aging skin by topically applying a composition comprising a Tiliacora triandra Diels plant extract capable of inhibiting collagenase activity.
It is highly desirable and it would be advantageous to have improved compositions and methods effective in protecting tissues comprising epithelial cells in general and skin in particular from deleterious effects caused by environmental hazards, particularly by pollutants.